glBegin(GL_TRIANGLE_FAN);glColor4f(0.0f, 0.0f, 0.0f,1.0f);glVertex2f(0.0f, 0.0f);    for(int i=0;i<N;++i){ pos_x=cos((i/180.0)*Pi+theta)*R;pos_y=sin((i/180.0)*Pi+theta)*R;glColor4f(0.0f, (i+0.01)/N, 0.0f,0.8f);glVertex2f(pos_x, pos_y); }glEnd();    

int power_of_two(int n)
{ if( n <= 0 ) return 0; return (n & (n-1)) == 0;
} GLuint load_texture(const char* file_name)
{ GLint width, height, total_bytes; GLubyte* pixels = 0; GLint last_texture_ID;GLuint texture_ID = 0; FILE* pFile = fopen(file_name, "rb"); if( pFile == 0 ) return 0; // 读取文件中图象的宽度和高度 fseek(pFile, 0x0012, SEEK_SET); fread(&width, 4, 1, pFile); fread(&height, 4, 1, pFile); fseek(pFile, BMP_Header_Length, SEEK_SET); // 计算每行像素所占字节数，并根据此数据计算总像素字节数
        { GLint line_bytes = width * 3; while( line_bytes % 4 != 0 ) ++line_bytes; total_bytes = line_bytes * height; } // 根据总像素字节数分配内存 pixels = (GLubyte*)malloc(total_bytes); if( pixels == 0 ) { fclose(pFile); return 0; } // 读取像素数据 if( fread(pixels, total_bytes, 1, pFile) <= 0 ) { free(pixels); fclose(pFile); return 0; } { GLint max; glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max); if( !power_of_two(width) || !power_of_two(height) || width > max || height > max ) { const GLint new_width = 256; const GLint new_height = 256; // 规定缩放后新的大小为边长的正方形
            GLint new_line_bytes, new_total_bytes; GLubyte* new_pixels = 0; // 计算每行需要的字节数和总字节数 new_line_bytes = new_width * 3; while( new_line_bytes % 4 != 0 ) ++new_line_bytes; new_total_bytes = new_line_bytes * new_height; // 分配内存 new_pixels = (GLubyte*)malloc(new_total_bytes); if( new_pixels == 0 ) { free(pixels); fclose(pFile); return 0; } gluScaleImage(GL_RGB, width, height, GL_UNSIGNED_BYTE, pixels, new_width, new_height, GL_UNSIGNED_BYTE, new_pixels); // 释放原来的像素数据，把pixels指向新的像素数据，并重新设置width和height
            free(pixels); pixels = new_pixels; width = new_width; height = new_height; } } glGenTextures(1, &texture_ID); if( texture_ID == 0 ) { free(pixels); fclose(pFile); return 0; } glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture_ID); glBindTexture(GL_TEXTURE_2D, texture_ID); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, pixels); glBindTexture(GL_TEXTURE_2D, last_texture_ID); free(pixels); return texture_ID;
} 

texGround = load_texture("xxxxx.bmp");

    glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, texGround); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, -0.5f,-0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, 0.5f,-0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, 0.5f,-0.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, -0.5f,-0.0f); glEnd();

    glDisable(GL_DEPTH_TEST);glEnable(GL_BLEND);